When Mark Springer was in middle school, he was a chubby guy who joked about his weight to mask the pain. “I didn’t know where to get good information [about weight loss],” he recalls. “The best I could come up with was, what if I just start doing what skinny people do? They must run. They probably eat a lot of salads.”

So in high school, he took up running. He joined the cross-country team and he dieted by not eating. Although he shed unwanted pounds, he became gaunt. “I was just skin and bones. I had no muscle,” he says. “I was like a stick.”

At Northwestern State University in Natchitoches, LA, where he played football, Springer figured out how to beef up with a different body composition. “It changed my life. It gave me so much confidence,” Springer adds. “It really did turn my life around.”

Springer started Avatar Nutrition three years ago to share what he’s learned -- and help others sidestep the pitfalls of mass-marketed fad diets. Today, at 28, Springer is CEO of Avatar Nutrition, which customizes dietary recommendations for each of its 24,000 users.

“Most people don’t know what the scientific methods are for losing fat,” says Springer, who partnered with Katie Coles, now the chief science officer.

Dieters suffer because their bodies learn to survive on fewer calories when they are on low-calorie diets, he says. When their metabolisms continue to slow down, the diets eventually becomes unsustainable. In those cases, he recommends a “reverse diet” to rev up the metabolism again.

“Metabolism can adapt in both directions,” he says. “It’s a survival mechanism.”

He says low-carb diets appear to be helpful by causing dieters to lose water weight. “Basically, you’re just peeing off all this body weight,” he explains. “It was never fat.”

While the Avatar’s program is nutritionally sound, it doesn’t require users to choose whole foods instead of fortified foods. “We’re not saying you shouldn’t eat whole foods. You’re not locked to them to be successful,” he says.

Avatar, which uses an app, charges $10 a month to gain access to the membership service. Members have access to a team of experts, such as a registered dietitian or certified strength and conditioning expert.

The program offers flexible dieting, which means there aren’t any no-nos. Users just adjust their protein, carbohydrate and fat requirements to include their favorite foods, or that piece of birthday cake.

“As your body changes, your needs for each of those micronutrients changes as well,” he says.

It takes the long-term, rather than short-term, approach to dieting. “It’s not just about what I can do in this six-week program,” he explains. “You have your entire life ahead of you. You need long-term thinking and planning to have results that stick.”

Avatar attracts users of all ages and walks of life, including women from a senior ladies ski club in Utah, nurses, and bartenders -- even a contingent of 200 from Singapore. “There’s almost like built in virality to it,” he explains.

Currently operating with a staff of 12, with a family-style office culture, Avatar is also employing four remote workers across the United States. “It’s a lot of fun. We kind of think of ourselves as a big family,” he says.

The company was growing so fast last summer they had to slow down the marketing. “The program is so effective that people using it are advertising it by word of mouth,” he says. “So many of our users are becoming walking billboards.”

Located on Northdale Boulevard in Carrollwood, Springer has decided to move to Austin, potentially next spring, to accommodate the company’s rapid expansion.

He is interested in Austin is for its commercial campuses that allow companies to grow to a few hundred employees in a building -- as well as for its favorable tax structure.

But his options are open for the time being. “I’m all ears for possibilities,” he says. “If Tampa and the region can offer incentives that are more enticing to stay ... then I want it.”